1. Field of the Invention
The present invention relates to semiautomatic pistols and, in particular, to fire control mechanisms for semiautomatic, double-action only pistols.
2. Discussion of Background
Semiautomatic pistols have been manufactured and used for decades. Improvements in semiautomatic pistols have increased their sophistication and effectiveness. Generally, these pistols are preferred by military and law enforcement personnel in the line of duty where a pistol must be accurate, reliable and safe to use. A pistol must be able to hit the target it is aimed at, to fire rounds repeatedly without jamming, and to fire only when the user intends to fire the pistol. Beyond these three basic concerns, a pistol should also be durable, have good balance, be easy to operate and service, be simple and inexpensive to manufacture, and have consistent, reasonable trigger-pull characteristics.
A semiautomatic pistol captures and utilizes part of the energy released from the firing of one round to load the next round into the firing chamber. Usually, the energy taken up by the recoil of a slide is used to push the next of a series of rounds into the firing chamber. The slide is part of one of a pistol's component groups that includes the barrel and breech block. In addition to the slide, a semiautomatic pistol has other component groups. There is the frame that includes the handle and trigger guard. The handle may be hollow in order to receive a clip containing a number of rounds of ammunition. The rounds are fed one at a time into the breach block. Finally, there is the fire control system which includes the trigger, the trigger bar, the sear, the striker, and the striker spring. Some fire control systems include a hammer as part of the fire control group.
Typically, the trigger is connected to the sear through the trigger arm. In pistols without hammers, pulling on the trigger between a forward and a rearward position causes the sear to release the striker, which is loaded against the striker spring, whereupon the striker is propelled forward toward the chambered round. The firing pin on the end of the striker strikes the primer on the shell casing of the chambered round, causing it to detonate. In pistols with hammers, pulling on the trigger causes the sear to release the hammer, which is loaded by a spring, whereupon the hammer pivots forward, hitting the striker and driving it toward the round in the chamber.
When the round detonates, chemical energy of the gun powder in the shell is converted to kinetic energy of the bullet, and the bullet is propelled from the casing through the barrel and out the muzzle of the pistol. The forward momentum of the propelled bullet is equaled by the rearward momentum of the pistol, which is partially absorbed as recoil of the slide. That recoil is controlled by a spring that returns the slide to its pre-fired position. The recoil of the slide, including its complete motion rearward and forward following the firing of the pistol, is used to eject the bullet's now empty shell casing and to chamber a next round. It may also be used to cock or partially cock the striker in some semiautomatic pistols.
Some semiautomatic pistols are described as being "single action," meaning that the trigger pull only releases the striker, the recoil having been used to cock the striker. Other semiautomatics are "double action," meaning that the trigger pull cocks, or at least partially cocks, the striker and also releases the striker after it is fully cocked. Some double action pistols are not truly double action because the recoiling slide partially cocks the striker. In true double action, the recoiling slide does not cock the striker, so there is no loss of momentum of the slide as is the case with those pistols that are not true double action. A pistol that is double action has only one mode: one where pulling the trigger cocks the striker; the recoil of the slide, other than removing the spent shell casing and chambering the next round, serves only to take up the recoil of the pistol.
The relationship of the various parts of a fire control system have been the subject of considerable development. U.S. Pat. No. 5,386,659 issued to Vaid, et al. teaches a design for a semiautomatic, double-action pistol. Their pistol design includes a sear biased forward by a sear spring which must be tensioned along with the compression of the striker spring to cock the striker. On recoil after firing, the sear and striker move in parallel planes so that they are fully repositioned for the next firing cycle. Three interrelated patents issued to Glock: U.S. Pat. Nos 4,539,889, 4,825,744, and 4,893,546, describe a fire control system for an automatic pistol where the pistol is partially cocked on recoil. Pulling the trigger moves the striker rearward against the striker spring and through a critical position on the travel path of the striker to complete the cocking. Two springs are used to establish a cocking force: a stronger spring that will urge the striker forward for firing and a weaker spring urging it rearward in order to substantially reduce trigger force.
Other designs for pistols exist. However, there remains a need for an effective fire control system for a semiautomatic pistol that operates reliably and safely.